This invention relates to a fuel cell system having fuel cell stacks and its diagnosis system. More particularly, the invention relates to a fuel cell system using PEFC (Polymer Electrolyte Fuel Cells).
A method that divides a large number of cells constituting a fuel cell stack into a plurality of cell groups, measures an output voltage for each cell group and diagnoses an operating condition on the basis of a mean voltage of the output voltages, voltage fluctuation and the value of the output voltage for each cell group has been proposed as one of technologies for the fuel cell system and its diagnosis system. JP-A-2004-127915, for example, discloses in its Abstract a system having a cell monitor capable of monitoring a voltage of each cell group as a fuel cell system that is applied to an electric motor car.